An ultrasonic transducer may be formed by making a piezoelectric resonant by forming electrodes on both sides of a piezoelectric element or by coupling a case to a piezoelectric resonant. If an electric pulse is applied to the electrodes of the piezoelectric resonant, the piezoelectric element resonates to generate ultrasonic wave.
Electric characteristics of an ultrasonic transducer are generally determined depending on material, shape, thickness, etc., of a piezoelectric element, and may be altered by an outer case, thickness of an adhesive layer, an operating environment, or adhesive material. Electric characteristics of an ultrasonic transducer may include a resonance frequency, an antiresonance frequency, a phase, an impedance, or the like, and if an electric pulse having the same frequency with the resonance frequency is applied to an ultrasonic transducer, the greatest ultrasonic wave energy may be output. The reason why an ultrasonic transducer outputs the greatest ultrasonic wave energy at the resonance frequency is that an impedance of an ultrasonic transducer is lowest at the resonance frequency. However, even if an electric pulse is applied with the resonance frequency, the output of the ultrasonic transducer may not be at the maximum value depending on characteristics of an electric pulse generating device. The reason of this is that the impedances of the electric pulse generating device and an ultrasonic transducer are different from one another, and this is caused by the fact that the maximum electric power is transmitted when the impedances of an electric power supplier and a load. Accordingly, in order to obtain the maximum ultrasonic wave output in an ultrasonic transducer, impedances together with the resonance frequencies should be matched with one another. For this function, impedance matching circuits may be additionally provided to an ultrasonic transducer and an electric pulse generating device.
However, since the electric characteristics of an ultrasonic transducer are altered very sensitively depending on various parameters as described above compared to an electric pulse generating device, it is difficult to perform the impedance matching. In particular, in case that an ultrasonic transducer is frequently replaced due to various reasons such as a life span, a disorder, or the like while the same electrical pulse generating device is used, it is much more difficult.
Recently, while ultrasonic wave is variously used in medical devices such as an ultrasonic wave stimulator, a high intensity focused ultrasonic device, frequency and energy of an ultrasonic wave become greater, so many techniques for increasing and stabilizing the output of the ultrasonic wave energy are being developed.
Generally, in order to increase a resonance frequency and an output intensity of an ultrasonic transducer, electrical connections such as a resonance frequency and an impedance matching are important together with physical conditions such as suitable material and shape of a piezoelectric element. However, as stated above, it is very difficult to manufacture an ultrasonic transducer having uniform electrical characteristics such as a resonance frequency and an impedance. Furthermore, in case that a resonance frequency of an ultrasonic transducer is high, a structure thereof is complicated, or an output intensity of ultrasonic wave is high, it is much more difficult to make characteristics of an ultrasonic transducer uniform. Due to such difficulties in a manufacturing process, ultrasonic transduces which have manufactured to have the same characteristics may actually have different characteristics. These differences may exert a bad influence on reactivation and treatment effect of the device. Although electrical characteristics are adjusted by adding impedance matching circuits to respective ultrasonic transducers, time for adding an impedance matching circuit is needed and manufacturing cost is increased.